The present invention relates generally to devices fabricated on thin silicon films, and more specifically the invention pertains a process for fabricating radiation-resistant silicon substrate devices grown on insulating diamond films.
Recently there has been increased interest in recrystallizing thin layers of semiconductor material, especially silicon, on a buried noncrystalline insulator layer as in, semiconductor-on-insulator technology. Typically, a layer of insulator material is formed on a semiconductor substrate and next, a layer of semiconductor material, is deposited thereover. The semiconductor layer is melted in whole or in part, and one or more solidification fronts are caused to advance laterally across the semiconductor layer.
Electronic devices based on buried insulator structures offer promise of, increased dielectric isolation, useful in, high voltage-high power devices, reduced parasitic capacitance in integrated circuits, and of improved radiation hardness of devices. Common buried insulator is silicon dioxide. While these devices have proven excellent, the search continues for radiation resistant silicon substrate devices, which could operate at high temperatures.
A promising buried insulator candidate is diamond. Diamond films have a resistivity of 10.sup.16 ohm-cm, and are excellent electrical insulators. The task of producing a recrystallized silicon layer on diamond device is alleviated, to some extent, by the systems disclosed in the following U.S. Patents, the disclosures of which are incorporated herein by reference.
U.S. Pat. No. 5,186,785 issued to Annamalai; PA1 U.S. Pat. No. 5,155,559 issued to Humphreys et al; PA1 U.S. Pat. No. 5,131,963 issued to Ravi; and PA1 U.S. Pat. No. 5,122,509 issued to Beetz, Jr. et al.
The patents listed above, relate to silicon-on--diamond (SOD) structures and processes to produce SOD structures. In particular, the Annamalai patent describes a process for fabricating radiation resistant silicon substrate based devices of zone melted, recrystallized silicon on diamond insulator films. The process begins by growing a 0.5 micron thick or a suitable thickness diamond insulating film on a silicon wafer such that the wafer has an exposed outer rim which circumscribes the diamond film. Next, a polysilicon coating is deposited over the diamond so that the polysilicon coating contacts the rim of the silicon wafer. Exposure of the wafer to heat at temperatures of 1,400 degrees Centigrade recrystallizes the polysilicon coating into a single recrystallized silicon crystal. After the zone melted recrystallization treatment is administered, the rim of the silicon wafer is removed to complete the recrystallized silicon-on-diamond wafer.
The Humphreys et al. Patent is directed to a rectifying contact comprising a Semiconducting diamond layer for forming a rectifying contact therewith, and an annealed interface region between the semiconducting diamond layer and the refractory metal silicide layer. The invention also provides a method for making a rectifying contact on a semiconducting diamond layer comprising the steps of forming a refractory metal silicide on the semiconducting diamond layer, and annealing the refractory metal silicide and diamond layer. The step of annealing comprises the step of heating the diamond layer and refractory metal silicide to a temperature of up to 1100 degrees Centigrade.
The Ravi patent relates to semiconductor elements comprising a single crystal layer of silicon on a diamond insulator. A basic element is formed by diffusing into one surface of a substrate an etch stop material to form a diffusion prepared layer. A silicon layer is epitaxially deposited onto the diffusion prepared layer of the substrate. A diamond layer is deposited onto the epitaxial silicon layer, followed by a polysilicon layer of about 20 mils thick and the substrate is removed by an etching process. The diffusion prepared layer is then removed to retain the epi silicon layer on-diamond.
The Beetz, Jr. et al patent describes a multilayer superconducting thin film composite article, comprising a carbon-containing substrate, an interlayer, and an overlayer comprising an HTSC material. The carbon-containing substrate preferably comprises diamond, and the interlayer preferably comprises a zirconium carbide sub-layer of zirconium metal and an outer sub-layer of zirconium oxide at the interface with the HTSC material overlayer. The interlayer accommodates formation of the superconducting film in an environment at elevated temperature without destruction of the substrate, while at the same time protecting the HTSC material in the overlayer from deleterious reaction with the substrate which otherwise may cause the HTSC material or precursor thereof to be highly resistive. While the above-cited references are instructive, a need remains for processes for fabricating Silicon-On-Diamond structures. The present invention is intended to satisfy that need.